Vibration isolation systems have been extensively used to provide vibration isolation for ground-based, airborne, and space-borne payloads. Vibration isolation systems provide a reduced vibration environment for a payload by isolating disturbances and vibrations between a top platform 102 and a supporting base 106 of the vibration isolation system (i.e., the mounting interface). As illustrated in FIG. 1, an exemplary vibration isolation system 100 consists of the top platform 102 for supporting a payload 104, and the supporting base 106 coupled to the top platform with a plurality of variable length vibration isolator struts 68. In an exemplary hexapod configuration as illustrated in FIG. 1, for example, six vibration isolator struts on three vibration isolation bipods 110 are connected in non-parallel pairs to the supporting base 106 by a plurality of mounting brackets 12a, crossing over to six opposed mounting brackets 12b on the top platform. The top platform can be moved in six degrees of freedom (three rotations, three translations) by changing the length of the variable length vibration isolation struts.
A conventional mounting system for each vibration isolator strut in the vibration isolation system includes hard mounting the vibration isolator strut between a pair of opposed brackets. As used herein, the term “hard mounting” or variations thereof refers to physical attachment of a first axial end portion of the vibration isolator strut to a mounting bracket attached to the supporting base and physical attachment of the second axial end portion of the vibration isolator strut to an opposed mounting bracket attached to the top platform (i.e., the pair of opposed brackets) by conventional fastening assemblies. A conventional fastening assembly comprises at least one threaded fastener passing through an opening in the respective mounting bracket and into the associated axial end portion of the vibration isolator strut, each threaded fastener being surrounded by a pair of spherical washers comprising a first spherical washer and a second spherical washer. The first spherical washer is placed between the respective mounting bracket and the axial end portion of the vibration isolator strut and the second spherical washer is placed between the fastener head and the mounting bracket. The pair of spherical washers and one or more shims disposed between the first spherical washer and the axial end portion of the vibration isolator strut fasten the respective axial end portion of the vibration isolator strut to the associated mounting bracket and at least partially correct for up to several degrees of misalignment between the mounting bracket and the vibration isolator strut. Structural members other than vibration isolator struts, such as for example, truss type structures are also hard mounted in conventional mounting systems between a pair of opposed mounting brackets in the same manner.
There are several disadvantages to hard mounting of structural members including vibration isolator struts. As the shims are only available in set sizes and because of variations among structural members, there is typically at least some strain on the structural member when conventionally hard mounted. Shims also add to the parts list for such conventional mounting systems. Additionally, once the structural member has been hard mounted to the pair of mounting brackets, the fastener heads are relatively inaccessible, making adjustments in conventional mounting systems difficult and time-consuming. Other types of mounting assemblies for vibration isolator struts (e.g., those including adjustable spherical mounts) are susceptible to small amounts of undesirable motion (“micro-motion”) between mounting assembly components (e.g., the mounting bracket and the fastening assembly) even after the fastener has been tightened. For vibration isolator struts, such micro-motion is an undesirable source of wear that can degrade alignment and/or stability of the vibration isolator struts over time, and reduce their useful life.
Accordingly, it is desirable to provide improved mounting systems for structural members, fastening assemblies thereof, and vibration isolation systems including the same. It is also desirable that exemplary embodiments permit structural members to be quickly and easily installed without using shims and adjusted to their zero strain position while allowing access to fasteners for making necessary mounting adjustments. It is also desirable that exemplary embodiments permit mounting assembly components to be clamped together substantially preventing micro-motion therebetween. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.